This invention relates to methods for making high aspect ratio nanocone structures that can be used to imprint nanoscale patterns on glass in an integrated glass manufacturing system.
Nanostructured surfaces have been widely studied for their superior optical and wetting properties such as antireflection and superhydrophobicity/hydrophilicity [1, 2, 3]. Due to their subwavelength feature size, such nanostructures behave as an effective medium with gradually varying index of refraction. Such a surface can be used to suppress Fresnel reflection at material interfaces, thereby acting as an antireflection surface and allowing broadband light to pass through without reflection losses [4]. In addition, both hierarchical roughness from those structures and the intrinsic chemical property of the surfaces can induce artificial super hydrophobicity and/or superhydrophilicity which can be applied as self-cleaning and anti-fogging surfaces, respectively [5,6].
Although these notable properties of multi-functional surfaces are well understood, fabricating defect-free nanostructured surfaces with multiple functionalities remains a difficult engineering challenge as a result of limitations of existing nanofabrication methods. The performance of these nanostructured surfaces are determined by their geometry. It is thus necessary to fabricate gradually tapered structures with small feature sizes (Λ) and large height (H). The higher the aspect ratio (H/Λ) the structures have, the better the optical and wetting properties they exhibit [7].
Nanostructured surfaces can be prepared by several existing fabrication methods such as electron beam lithography [8], nanoimprint/polymer replication [9], deposition of multilayer porous films or chemical materials [10], and colloidal lithography [11]. However, it is difficult to achieve high aspect ratio structures (greater than five) with a gradual tapered profile using prior art techniques. That is to say, the properties of subwavelength nanocone structures fabricated using existing techniques have limited performance.
Natural materials often have hierarchical structures on their surfaces. For example, a lotus leaf [5, 14] has hierarchical microstructures on its surface which keeps the plant clean for photosynthesis. These structures employ both material and geometric effects to render the surface superhydrophobic, thereby allowing water droplets to form spherical beads to remove surface particle contaminants. Using similar design principles it is possible to engineer a textured superhydrophobic surface that can self-clean. Such nanostructures can also be rendered superhydrophilic by controlling the surface treatment thereby allowing the surface to be anti-fogging.
By understanding these nature-inspired principles, it is possible to design surfaces that have combined wetting (self-cleaning and/or anti-fogging) and optical (antireflection, lossless transmission) properties. Using advanced lithography and multiple plasma etching processes, the methods disclosed herein are able to produce glass that is anti-glare, near-perfect transmitting, and selectively self-cleaning and/or anti-fogging.
It is therefore an object of the present invention to disclose methods for making high aspect ratio nanocone structures and using the structures to imprint a pattern during glass manufacture.